Bathing vessels such as showers and bathtubs have surrounds that are subject to stresses. The walls may support grab bars and towel bars, and users may interact with the walls of the surrounds by stressing them.
Bathing vessels may be manufactured from a variety of different materials, such as plastic materials. Plastic bathing vessels, however, must meet certain minimum performance requirements. For instance, the American National Standards Institute (ANSI) sets forth minimum physical requirements and testing methods for plastic bathtub and shower units. A bathing vessel that meets the requirements is approved for use in homes, buildings or other structures as a plumbing fixture.